The voltage of a battery represents the force that makes electrons flow through a current in an electrical circuit. It measures potential energy, which is the amount of energy available to move electrons from one point to another in the circuit. The actual flow of the electrons through the circuit can be impeded by an opposing force called resistance. To calculate the amount of voltage a battery can provide, a mathematical formula is all you need.

Write out the formula to calculate the amount of voltage present in a circuit. The voltage present is equal to the amount of resistance times the current. The formula is: Voltage (E) = Current (I) x Resistance (R), or E = IR.

Substitute the values for the current and resistance for the variables in the equation. Current is measured in amperes, and resistance is measured in ohms. For example, if the the current were 6 amperes and the resistance were 3 ohms, the equation would be:

E = (3)(6).

Solve the equation for the amount of voltage, E. If the resistance were 3 ohms and the current were 6 amperes, the voltage supplied by the battery in this circuit would be 18 volts.